The field of the invention relates to specimen collection tubes and stoppers therefor.
Blood collection tubes typically have straight side walls which terminate in an open end adapted for receiving a resilient stopper. The input end of the stopper usually is tapered to facilitate its insertion within the tube. Because of the angle the taper forms with the interior walls of the tube, a crevice is created in which blood can flow and cling. Centrifuging the tube does not always remove this blood deposit. It must therefore be wiped off laboriously to avoid contaminating the specimen. Even an untapered stopper may tend to attract blood which may be difficult to spin down.
Another problem arises from the fact that some stoppers contain slots along the outside surfaces of their side walls to serve as vent ports aiding evacuation. The slot can be a problem if additives are to be included within the tube as such additives may be entrapped therein during storage and handling. Blood deposits may also be retained in the slot.